Devices for amusing and exercising domestic animals such as cats are in wide usage. Many of the known devices include endless tracks along which a ball may be propelled by a cat and a pad of material which the cat may claw. Some of the known devices have a ball-accommodating track which opens toward the interior of the device, whereas others have such tracks opening upwardly. In either case the stacking of one device upon another prevents access to visibility of more than a single track.
Many households have more than one cat. Since more than one cat may wish to use the device at the same time, it is desirable to provide stackable devices which will enable each cat to have access to a different track so as to propel the ball therein independently of the other cat or cats. However, in those instances in which the pet owner does not desire more than one device, it is desirable to provide a device which offers no obstruction to the free use of the device by a single cat.